How many days can the Twisted Waters World Change last?

Question

So, I'm on a world where there aren't too much achievement hunters and charlovers, so Lake Equivocolao never got dirty. I'm throwing the necessary 1000 corpses today, and will catch a Shimmer Swimmer tomorrow. I know there is also a 20 hour cooldown to catch another Shimmer Swimmer, but since I'm aiming for the "Biodegradable" Achievement, I would like to know:

Does the Lake remains dirty if 1000 fish are not caught? How long does it remains dirty? Is there a limit of days or it is only based on the number of fishes?

Let's say I'm the only one doing this achievement and fishing Shimmer Swimmers, will I complete this achievement in 50 days (not counting the 20h, but 24h instead) if I keep fishing everyday? Or will I need to keep dumping corpses into the Lake every 2-3 days?

Comments

I've seen the lake remain dirty for about 3 days. So, I think that as long as the necessary amount of fish is not caught, it should remain dirty.